« Rôle de l'influence sociale sur l'interprétation de l'information comptable : une expérimentation »

International audienceL'influence sociale peut être mise en évidence lorsqu'un sujet abandonne sa propre analyse d'une société afin de suivre le consensus des analystes. Grâce à une situation expérimentale proche de celle employée par Cote et Sanders (1997), différentes hypothèses sur la genèse de ce comportement sont testées. Il est soumis aux sujets des informations comptables et financières d'une société afin qu'ils émettent une recommandation d'achat ou à de vente. Ce jugement personnel est ensuite confronté à un consensus d'analystes qui s'oppose à cette recommandation, afin d'étudier si les sujets révisent cette dernière. Le résultat principal est que les sujets sont influencés et certains imitent, en s'opposant à leur propre jugement comptable et financier de la société, et ce d'autant plus qu'ils sont incertains dans leurs capacités à correctement analyser la société. Lorsque la notion de réputation est introduite, les sujets conformistes ont plus tendance à suivre le consensus. En revanche, les sujets ne semblent pas être significativement influencés par la fiabilité perçue de l'information, la confiance dans le consensus des analystes ni la proportion de la majorité dans le consensus

Next-to-next-to-leading order spin-orbit effects in the equations of motion of compact binary systems

We compute next-to-next-to-leading order spin contributions to the post-Newtonian equations of motion for binaries of compact objects, such as black holes or neutron stars. For maximally spinning black holes, those contributions are of third-and-a-half post-Newtonian (3.5PN) order, improving our knowledge of the equations of motion, already known for non-spinning objects up to this order. Building on previous work, we represent the rotation of the two bodies using a pole-dipole matter stress-energy tensor, and iterate Einstein's field equations for a set of potentials parametrizing the metric in harmonic coordinates. Checks of the result include the existence of a conserved energy, the approximate global Lorentz invariance of the equations of motion in harmonic coordinates, and the recovery of the motion of a spinning object on a Kerr background in the test-mass limit. We verified the existence of a contact transformation, together with a redefinition of the spin variables that makes our result equivalent to a previously published reduced Hamiltonian, obtained from the Arnowitt-Deser-Misner (ADM) formalism.Comment: 38 pages, minor changes to match the published versio

Next-to-leading tail-induced spin-orbit effects in the gravitational radiation flux of compact binaries

The imprint of non-linearities in the propagation of gravitational waves --- the tail effect --- is responsible for new spin contributions to the energy flux and orbital phasing of spinning black hole binaries. The spin-orbit (linear in spin) contribution to this effect is currently known at leading post-Newtonian order, namely 3PN for maximally spinning black holes on quasi-circular orbits. In the present work, we generalize these tail-originated spin-orbit terms to the next-to-leading 4PN order. This requires in particular extending previous results on the dynamical evolution of precessing compact binaries. We show that the tails represent the only spin-orbit terms at that order for quasi-circular orbits, and we find perfect agreement with the known result for a test particle around a Kerr black hole, computed by perturbation theory. The BH-horizon absorption terms have to be added to the PN result computed here. Our work completes the knowledge of the spin-orbit effects to the phasing of compact binaries up to the 4PN order, and will allow the building of more faithful PN templates for the inspiral phase of black hole binaries, improving the capabilities of ground-based and space-based gravitational wave detectors.Comment: 22 pages, 1 figure; replaced to match the published version, two references adde

Gestion des résultats comptables et structure de l'actionnariat : le cas français

International audienceThe aim of our research is to study the impact of ownership structure on earnings management among French listed companies. The study is performed on a sample of SBF 250 listed companies over the 2004-2008 period. The ownership concentration, measured by the three largest shareholders, appears to reduce earnings management. As far as the type of ownership is concerned, analyses pinpoint the influence of three types of shareholders. First, the presence of the state as shareholder tends to increase the intensity of earnings management. Moreover, the weight of family and industrial ownership limits the intensity of earnings management. One explanation could be in the long-term investment horizon of these agents, which does not induce executives to perform earnings management.L'objectif de notre recherche est d'étudier l'impact de la structure de l'actionnariat sur la gestion du résultat des sociétés cotées françaises. L'étude est conduite sur un échantillon de sociétés cotées de l'indice SBF 250 sur la période 2004-2008. La concentration de l'actionnariat, mesurée par les trois premiers actionnaires, semble limiter la gestion du résultat. Concernant le type d'actionnariat, les analyses laissent apparaître l'influence de trois catégories d'actionnaires. Tout d'abord, la présence de l'Etat comme actionnaire semble accentuer l'intensité de la gestion du résultat. Par ailleurs, le poids des actionnaires familiaux et industriels limite l'intensité de la gestion du résultat. Une explication pourrait être dans l'horizon de placement à long terme de ces acteurs, qui n'incite pas les dirigeants à ce type de gestion

The third and a half post-Newtonian gravitational wave quadrupole mode for quasi-circular inspiralling compact binaries

We compute the quadrupole mode of the gravitational waveform of inspiralling compact binaries at the third and a half post-Newtonian (3.5PN) approximation of general relativity. The computation is performed using the multipolar post-Newtonian formalism, and restricted to binaries without spins moving on quasi-circular orbits. The new inputs mainly include the 3.5PN terms in the mass quadrupole moment of the source, and the control of required subdominant corrections to the contributions of hereditary integrals (tails and non-linear memory effect). The result is given in the form of the quadrupolar mode (2,2) in a spin-weighted spherical harmonic decomposition of the waveform, and may be used for comparison with the counterpart quantity computed in numerical relativity. It is a step towards the computation of the full 3.5PN waveform, whose knowledge is expected to reduce the errors on the location parameters of the source.Comment: 19 pages, 1 figure; minor corrections, including some rephrasing in the introduction and in section III

Surrogate model for an aligned-spin effective one body waveform model of binary neutron star inspirals using Gaussian process regression

Fast and accurate waveform models are necessary for measuring the properties of inspiraling binary neutron star systems such as GW170817. We present a frequency-domain surrogate version of the aligned-spin binary neutron star waveform model using the effective one body formalism known as SEOBNRv4T. This model includes the quadrupolar and octopolar adiabatic and dynamical tides. The version presented here is improved by the inclusion of the spin-induced quadrupole moment effect, and completed by a prescription for tapering the end of the waveform to qualitatively reproduce numerical relativity simulations. The resulting model has 14 intrinsic parameters. We reduce its dimensionality by using universal relations that approximate all matter effects in terms of the leading quadrupolar tidal parameters. The implementation of the time-domain model can take up to an hour to evaluate using a starting frequency of 20Hz, and this is too slow for many parameter estimation codes that require $O(10^7)$ sequential waveform evaluations. We therefore construct a fast and faithful frequency-domain surrogate of this model using Gaussian process regression. The resulting surrogate has a maximum mismatch of $4.5\times 10^{-4}$ for the Advanced LIGO detector, and requires 0.13s to evaluate for a waveform with a starting frequency of 20Hz. Finally, we perform an end-to-end test of the surrogate with a set of parameter estimation runs, and find that the surrogate accurately recovers the parameters of injected waveforms.Comment: 19 pages, 10 figures, submitted to PR

Post-Newtonian prediction for the (2,2) mode of the gravitational wave emitted by compact binaries

We present our 3.5PN computation of the (2,2) mode of the gravitational wave amplitude emitted by compact binaries, on quasi-circular orbits and in the absence of spins. We use the multipolar post-Newtonian wave generation formalism, extending and building on previous works which computed the 3PN order. This calculation required the extension of the multipolar post-Minkowskian algorithm, as well as the computation of the mass source quadrupole at 3.5PN order. Our result will allow more accurate comparisons to numerical relativity, and is a first step towards the computation of the full 3.5PN waveform amplitude, which would improve the estimation of the source parameters by gravitational wave detectors.Comment: 5 pages; proceeding of the 9th LISA Symposium, Pari